mesa: extend GLSLZeroInit semantics
This commit introduces a new way to zero-init variables but keep the
old one to not break any existing behavior.
With this change GLSLZeroInit becomes an integer, with the following
possible values:
- 0: no 0 init
- 1: current behavior
- 2: new behavior. Similar to 1, except ir_var_function_out type are
0 initialized but ir_var_shader_out.
The rationale behind 2 is: zero initializing ir_var_shader_out can
prevent some optimization where out variables are completely eliminated
when not written to.
On the other hand, zero initializing "ir_var_function_out" has no
effect on correct shaders but typically helps shadertoy since the main
function is:
void mainImage(out vec4 fragColor) { ... }
So with this change we're sure that fragColor will always get a value.
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4607>
4 files changed